The structure of the 12 S globulin from rapeseed (Brassica napus L.)

Abstract

The 12 S globulin of rapeseed represents an oligomeric protein with a molecular weight of 300,000. It is composed of 6 subunits, which are arranged in a trigonal. antiprism with the point group symmetry 32 (D3).Each subunit contains smaller units (polypeptide chains) with molecular weights in the range of 18,500 to 31,000. The protein contains the following 4 polypeptide chains differing by their molecular weights in the SDS-electrophoresis: 18,500 k 800, 21,100 500, 26,800 900, 31,200 k 1,600.According to its quaternary structure the protein dissociates under milieu conditions : low ionic strength extremely high or low pHThe secondary structure of the protein is characterized by a low (1 1 yo) content of a-helix and a relatively high (31 %) content of &conformation.11/12 S globulins in the seeds of different plant species and botanical families.Owing to its structure and physico-chemical properties the rapeseed protein is closely related to otherThe 12 S globulin represents a main storage protein in the seeds of Brassica species [I -61. 21-33% of the nitrogen in sodium chloride extracts of defatted rapeseed varieties or 18-28The globulin was first isolated by BHATTY et al.[I] from oil-free rapeseed meal by extraction with 10 % sodium chloride, precipitation by dialysis against water, and chromatographic separation on Sephadex G-100. SIMARD et al. 191 used the technique of fractionating precipitation and dissolution by ammonium sulphate for the isolation of the protein. SCHWENKE et al. [lo] described a combined gel and ionic-exchange chromatographic purification of the 12 S globulin. The present paper summarizes the results of research on the physico-chemical properties and structure of the 12 S globulin of rapeseed. of the total seed nitrogen correspond to this protein [l, 7, 81. Hydrodynamic properties and molecular weightAfter isolation and purification of the protein BHATTY et al.[l] could show by ultracentrifugal analysis that this rapeseed globulin, owing to its sedimentation property, corresponds to the group of 11/12 S seed proteins. The authors found a sedimentation coeffi-

Characterization of Radish (Raphanus sativus) Storage Proteins

“…SDS-polyacrylamide gel electrophoresis, and amino acid composition studies confirm previous observations on rapeseed and other related species (3,5,11,12,14,15,19,21,26,27). However, the use of two-dimensional gel electrophoresis systems provides new information.…”

Rapeseed use in aquaculture

“…Napin is composed of two polypeptide chains with molecular weights of 9 and 4 kDa, linked by disulfide D105, page 5 of 9 bonds. Cruciferin is consisted of 6 subunits and each subunit contains smaller units (polypeptide chains) with molecular weights in the range of 18.5 to 31.2 kDa, linked by disulfide bonds (Schwenke et al, 1973;Schwenke et al, 1983;Mieth et al, 1983;Schwenke, 1990). Based on the SDS-PAGE assay the both storage proteins were observed in the produced protein product concerning the detected bands with molecular weights of 31-29, 24-21 kDa for cruciferin polypeptide chains and 9-4 kDa for napin polypeptide chains.…”

Application of new methodology to canola protein isolation

“…It was found, using geI chromatography studies, that coagulation was manifested by unfolding of the protein under these conditions. Any contradictions concerning the molecular weight of the rapeseed 12S globulin have been addressed and subsequently clarified by Schwenke et al (1983). Schwenke and his co-workers have determined the molecular weight of Lhe 12S gtobulin to acLually be 300,000 + I0,000 g/mol (laieth et al, 1983;Schwenke et a1,., 1983;Schwenke et al-.'…”